<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    *{
      margin: 0px;
      padding: 0px;
    }
    html,body{
      width: 100%;
      height: 100%;
    }
    body{
      background-color: pink;
      display: flex;
      flex-direction: row;
      align-items: center;
      justify-content: center;
    }
    .heart{
      width: 200px;
      height: 200px;
      background-color: red;
      position: relative;
      transform: rotate(45deg);
      animation: heartbit 1s linear 0s infinite alternate;
      box-shadow: 0 0 30px red;
    }
    .heart::before{
      content: "";
      width: 200px;
      height: 100px;
      background-color: red;
      position: absolute;
      left: 0;
      top:-99px;
      border-radius: 100px 100px 0 0;
      box-shadow: 0 0 30px red;
    }
    .heart::after{
      content: "";
      width: 100px;
      height: 200px;
      background-color: red;
      position: absolute;
      top: 0;
      left: -99px;
      border-radius: 100px 0 0 100px;
      box-shadow: 0 0 30px red;
    }

    @keyframes heartbit {
      0%{
        transform: rotate(45deg); scale:calc(0.6);
      }
      100%{
        transform: rotate(45deg); scale:calc(1.4);
      }
    }

  </style>
</head>
<body>
  <div class="heart"></div>
</body>
</html>